Here's a relatively detailed Radio World story on the Durst LLC broadcasting facility prep in the new 1WTC building, for which they have not yet secured any tenants.

“We are looking at a broadband FM antenna that could easily accommodate all of the radio broadcasters who lost facilities at the World Trade Center,” Lyons said. Some broadcasters with extremely directional signals could be accommodated with individual antennas.

Design features for the transmission facility are complete but no orders have been placed for transmission hardware, he said.

“We are waiting to see if we get commitments before moving forward and ordering transmission line and combiners. We need to make sure the project is financially viable before moving forward. We are lining up tours for broadcasters right now. We also are meeting with several antenna manufacturers to determine who we go with.”

Durst, for those not playing the home game (I wasn't) is the operator of the 4 Times Square facility a number of Empire State Building tenants use as their backup.